THE INFLUENCE OF REDUCTIVE DISSOLUTION OF IRON OXIDES BY S(-II) ON URANIUM MOBILITY


V. G. Alexandratos
T. Behrends
P. Van Cappellen
Résumé

This study investigates possible redox transformations of uranium under Ntransient redox conditions. NSpecific focus lies on the fate of U as reductive dissolution of iron oxyhydroxides by S(-II) is initiated. In batch experiments sulfide was incrementally added to a lepidocrocite suspension containing adsorbed U(VI). The partitioning of uranium was monitored during the progressing transformation of lepidocrocite into FeS. Synchrotron-based X-ray absorption spectroscopy was used to resolve the oxidation state of uranium.Upon addition of sulfide intermediate release of U from the solid to the solution was observed. The mobilization of U was followed by immobilization in later stages. XAS reveals that this immobilization coincides with reduction of NU(VI) to U(IV). Consequently, reduction of U(VI) and precipitation of U(IV) solids, due to a shift from oxic to sulfate reducing conditions is possible. NHowever, kinetic effects might lead to an intermediate mobilization of U that should be considered for the risk assessment of nuclear waste repositories and the remediation of sites, contaminated with radionuclides.

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  • Geochemistry and Ore Deposit Geology
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Références
Afornso, M., dos Santos and Stumm Werner, 1992. Reductive Dissolution of Iron(III) (Hydr)oxides by
Hydrogen Sulfide. Langmuir, 8, 1671-1675.
Anderson, RF, Fleisher, MQ., LeHuray, AP., 1989. Concentration, oxidation state and particulate flux of
uranium in the Black Sea. Geochim. Cosmochim. Acta, 53, 2215-2224.
Bargar, J. R., Reitmeyer, R., Lenhart, J. J and Davis, J.A., 2000. Characterization of U(VI)-carbonato ternary
complexes on hematite: EXAFS and electrophoretic mobility measurements. Geochimica et
Cosmochimica Acta, 64, No. 16, pp. 2737–2749, 2000.
Behrends, T. and Van Cappellen, P., 2005. Competition between enzymatic and abiotic reduction of ura-
XLIII, No 5 – 2316
Fig. 5: Chart with U(VI) percentages remaining in association with the solid from two suspensions reacted with 8
mM S(-II) in “C” and 5 mM S(-II) in “D”. Results are derived using coordination numbers from EXAFS fitting.
nium(VI) under iron reducing conditions. Chemical Geology 220, pp. 315-327.
Canfield, D.E., 1989. Reactive iron in marine sediments. Geochim. Cosmochim. Acta 53, 619–632
Chaillou, G., Anschutz, P., Lavaux, G., Schäfer, J. and Blanc, G., 2002. The distribution of Mo, U, and
Cd in relation to major redox species in muddy sediments of the Bay of Biscay. Marine Chemistry 80:
-59
Charlet, L., Silvester, E., and Liger, E., 1998c. N-compound reduction and actinide immobilisation in
surficial fluids by Fe(II): the surface Fe(III)OFe(II)OH degrees species, as major reductant. Chemical
geology, vol.151 iss.1-4, pg.85 -93.
De Pablo, J., Casas, I., Gimenez, J., Molera, M., Rovira, M., Duro, L., and Bruno, J., 1999. The oxidative
dissolution mechanism of uranium dioxide. I. The effect of temperature in hydrogen carbonate
medium. Geochim. Cosmochim. Acta 63, 3097-3103.
Duff, M.C. and Amrhein, C., 1996. Uranium(VI) adsorption on goethite and soil in carbonate solutions.
Soil Sci. Soc. Am. J. 60, 1393.
Fredrickson, J.K., Zachara, J.M., Kennedy, D. W., Duff, M. C., Gorby, Y. A., Li, S. M. W., and Krupka,
K.M., 2000. Reduction of U(VI) in goethite (alpha-FeOOH) suspensions by a dissimilatory metal-reducing
bacterium. Geochim. Cosmochim. Acta 64, 3085-3098.
Gabriel, U., Gaudet, J. P., Spadini, L., and Charlet, L., 1998. Reactive transport of uranyl in a goethite column:
an experimental and modeling study. Chem. Geol., 151, 107-28.
Giammar, D.E and Herring, J.G., 2001. Time scales for sorption-desorption and surface precipitation of
uranyl on goethite. Environ. Sci. Thechnol. 35, 3332-3337
Hsi C.-K. D. and Langmuir, D., 1985. Adsorption of uranyl onto ferric oxyhydroxides: Application of the
surface complexation site-binding model. Geochim. Cosmochim. Acta 49, 1931–1941.
Ho, C. H. and Miller, N. H., 1986. Adsorption of uranly species from bicarbonate solution onto hematite
particles. J. Colloid Interf. Sci. 110, 165–171.
Jørgensen, B. B., 1977. The sulfur cycle of a coastal marine sediment (Limfjorden, Denmark). Limnol.
Oceanogr. 5, 814–832.
Krom, M. D., Mortimer, R. J. G., Poulton, S. W., Hayes, P., Davies, I. M., Davison, W., and Zhang, H.,
In-situ determination of dissolved iron production in recent marine sediments. Aquatic Sciences
, 282-291.
Langmuir, D., 1978. Uranium solution-mineral equilibria at low temperatures with application to sedimentary
ore deposits. Geochim. Cosmochim. Acta 42, 547–569.
Liger, E., Charlet, L. and Van Cappellen, P., 1999. Surface catalysis of uranium (VI) reduction by iron(II).
Geochim. Cosmochim. Acta, 63, 2939-2955.
Lloyd, J. R., Chesnes, J., Glasauer, S., Bunker, D. J., Livens, F. R., and Lovley, D. R., 2002. Reduction of
actinides and fission products by Fe(III)-reducing bacteria. Geomicrobiology Journal 19(1), 103-120.
Lovely, D. R., Phillips, E. J. P., Gorby, Y. A., and Landa, E. R., 1991. Microbial reduction of uranium. Nature
, 413-416.
Lovley, D. R., Roden, E. E., Phillips, E. J. P., and Woodward, J. C., 1993. Enzymatic Iron and Uranium
Reduction by Sulfate-Reducing Bacteria. Mar. Geol. 113, 41–53.
Mohagheghi, A., Updegraff, D. M., Goldhaber, M. B., 1984. The role of sulfate-reducing bacteria in the
deposition of sedimentary uranium ores. Geomicrobiology Journal. 4(2): 153-173
Morrison, S. J., Spangler, R. R., and Tripathi, V. S., 1995a. Adsorption of U(VI) on Amorphous Ferric
Oxyhydroxide at High-concentrations of Dissolved Carbon (IV) and sulphur (VI). Journal of Contaminant
Hydrology 17, 333-346.